1. Field of Invention
The present invention relates generally to methods and apparatus for augmenting and manipulating objects by entering images of the objects into computer systems. More particularly, the present invention relates to capturing images of an object and entering those images into a computer system in an unencumbered manner.
2. Background
An increasingly important procedure in the field of computer image processing and manipulation is entering images of objects into a computer system so that a digitized version of the image exists for the computer to manipulate. One prevalent method for capturing an image of an object and entering it into a computer system is a procedure generally known as blue-screening.
Blue-screening, from the field of digital effects and chroma-keying, is used in the field of film and video editing by taking an object in one image, e.g. an input image, and compositing that object onto another image, e.g. a destination image, with minimal distortion of the object. For example, this procedure could be used for taking an object such as a human figure in one video and placing that human figure into another video without distorting or altering the image of the person. One video image may have a person standing or moving around in a typical living room and another video can be of an outdoor scene such as a jungle or desert. The compositing procedure would take the image of the human figure in the living room and place the figure in the other video thereby providing the effect of the human figure standing or moving around in the given outdoor setting.
This method is commonly referred to as blue-screening and involves placing a blue or other fixed-color screen behind the object being composited, typically the image of a person (the color blue is a hue that strongly contrasts all colors of human skin). In blue-screening, the system checks to see which pixels in the input image are not blue and labels those pixels as foreground pixels. Normally, the foreground pixels will only be those pixels that are part of the object being composited since there are typically no other objects in the image and the background is solid blue. The system then composites, or blends, the object (i.e. collection of all foreground pixels) onto a destination image. One of the disadvantages of using blue-screening for object compositing is that it requires a fixed color screen behind the object. Another disadvantage is that if any of the colors on the object, such as an item of clothing, is blue, holes will appear in the object in the destination image. This occurs because the pixels in the blue areas on the object will not be labeled as foreground pixels and thus will not be composited with the rest of the object, resulting in the object having holes when composited onto the destination image.
Another prior art method is electronic matting techniques originating from the film industry. In this procedure, an alpha image is a matte image.
The matte technique predates bluescreening, being the film version of the more modem electronic technique. A special film emulsion that is highly sensitive to one particular wavelength of light (in the blue part of the spectrum) is exposed to a scene illuminated by that color. The background of the scene is typically very reflective of this color, and the object(s) being isolated ("bluescreened") are significantly less reflective of this color. A black-and-transparent negative is thus produced that is opaque wherever it was exposed to the blue light. A second "holdout" negative is made directly from this one that is opaque where the first one was transparent, and vice versa. The filmed object is then exposed through the first matte negative in an optical printer, and the filmed background is double-exposed through the second negative, resulting in a composited "bluescreened" image.
Therefore it would be desirable to have a method and apparatus for capturing in real-time an image of an object to enter into a computer in such a way that minimizes formal human intervention with the computer and yet captures, in negligible time, a complete and clean-edged image of the object for the computer to manipulate or augment.